The primary goal of this project is to delineate the mechanism by which arrestin-2 regulates T cell chemotaxis in asthma. We previously showed that mice devoid of arrestin-2 do not develop allergic airway disease (AAD) and that T cell chemotaxis is impaired in these mice. Our preliminary data extend these observations to specifically show that Th2 cell chemotaxis is impaired in the absence of arrestin-2. Furthermore, we propose that the mechanism by which arrestin-2 positively regulates Th2 cell chemotaxis is through use of the novel arrestin-2-dependent signaling pathway. Our preliminary data also suggest that Th1 cell chemotaxis may be positively regulated by arrestin-2. Although not well understood, Th1 cells also contribute to the development of allergic inflammatory airway disease and thus, their regulation by arrestin-2 will be considered in this project. The schema to be addressed is: Agonist activation of chemokine receptor results in the assembly of a chemokine receptor/arrestin-2/MAPK signaling complex, which induces antigen-polarized T cell chemotaxis. Primary T cells that transgenically express an OVA-specific T cell receptor (TgTCR), replete with, and devoid of, arrestin-2, will be Th1- or Th2-polarized both in vitro and in vivo to test the hypotheses listed in the following Specific Aims: 1. To demonstrate that agonist binding of CCR4 leads to activation of a arrestin-2-dependent cell signaling mechanism in Th2 cells. 2. To demonstrate that the arrestin-2-dependent signaling pathway significantly promotes chemotaxis of allergen-activated [Th1 and Th2] cells. 3. To demonstrate that chemotaxis of [Th1 and Th2] cells from secondary lymphoid tissue to the lung is impaired in cells devoid of arrestin-2. We will use an in vivo competition transfer model where CD4+ T cells expressing an OVA-specific TCR are harvested from WT-TgTCR and arrestin-2-KO-TgTCR mice, fluorescently labeled with a stable intracellular dye, and transferred to a recipient mouse. Results from these aims will define key migratory routes for Th1 and Th2 cells in AAD, will define an arrestin-dependent chemokine receptor signaling pathway and will integrate these themes to show that arrestin-dependent signaling underlies the development of AAD. New concepts emanating from this research may provide new strategies for the treatment for asthma whereby therapeutics are developed that can selectively regulate arrestin-dependent signaling pathways, while leaving G protein-dependent signaling pathways untouched. Project Narrative: Asthma cannot be established unless T cells, a type of inflammatory cell, are able to migrate to the lung. Although detrimental in asthma, T cells are very important for immune defense against pathogens. Our work will provide information that could revolutionize asthma treatment by aiding the search for a therapeutic that can selectively prevent the deleterious migration of T cells while leaving their beneficial effects untouched.